Smoking articles, (e.g., cigarettes, cigars, pipes, etc) and smokeless tobacco products (e.g., chewing tobacco, snuff, etc.) are made from natural tobacco, reconstituted tobacco, and blends thereof. Reconstituted tobacco is a type of tobacco that is generally manufactured from natural tobacco by-products generated during the threshing of the natural tobacco leaf or during the manufacture of the tobacco article. However, some natural tobaccos, such as dark air cured, air cured, burley tobaccos, etc., may contain nitrosamines formed during the curing of tobacco, e.g., tobacco-specific nitrosamines (TSNAs) and non-tobacco-specific nitrosamines. Likewise, reconstituted tobacco formed from natural tobacco by-products may also contain nitrosamines. In addition, the smoke produced by tobacco products containing nitrosamines can also contain nitrosamines, which are either transferred from tobacco or pyro-synthesized in certain cases.
Extensive research has been conducted on nitrosamines and TSNAs, particularly in tobacco products. In many cases, it has been determined that such ingredients may be unwanted in the final tobacco product. For example, U.S. Pat. No. 5,810,020 to Northway, et al. describes a process for removing TSNAs from tobacco by contacting the tobacco material with a trapping sink, wherein the trapping sink comprises a select transition metal complex which is readily nitrosated to form a nitrosyl complex with little kinetic or thermodynamic hindrance.
Despite such attempted benefits to remove TSNAs from tobacco, a need currently exists for an improved method of reducing the content of nitrosamines (e.g., TSNAs) in tobacco. In particular, a need exists for an effective and relatively inexpensive method for reducing nitrosamines (e.g., TSNAs) in tobacco (e.g., natural tobacco, reconstituted tobacco, tobacco extracts, blends thereof, and other tobacco-containing materials) as well as tobacco products formed therefrom.
In accordance with one embodiment of the present invention, a method for reducing the content of nitrosamines in tobacco is disclosed. The method includes combining tobacco with a solvent (e.g., water and/or other compounds) to form a soluble portion. The soluble portion contains an initial total level of tobacco-specific nitrosamines per gram of the soluble portion. For instance, in one embodiment, the tobacco-specific nitrosamines are selected from the group consisting of Nxe2x80x2-Nitrosonornicotine, 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone, Nxe2x80x2-Nitrosoanatabine, and Nxe2x80x2-Nitrosoanabasine.
Once formed, the soluble portion is contacted with a nitrosamine-reducing material (e.g., adsorbent or absorbent) such that the resulting total level of the tobacco-specific nitrosamines per gram of the soluble portion is at least about 20% less than the initial total level of the tobacco-specific nitrosamines per gram of the soluble portion, and in some embodiments, at least about 60% less than the initial total level of the tobacco-specific nitrosamines, and in some embodiments, between about 85% to about 100% less than the initial total level of the tobacco-specific nitrosamines. For example, in some embodiments, the resulting total level of nitrosamines in the soluble portion is less than about 300 nanograms per gram of the soluble portion, and in some embodiments, less than about 40 nanograms per gram of the soluble portion.
In general, any material capable of reducing the amount of nitrosamines in tobacco can be utilized in the present invention. For instance, in one embodiment, the nitrosamine-reducing material is selected from the group consisting of charcoal, activated charcoal, zeolite, sepiolite, and combinations thereof. Further, the nitrosamine-reducing material may also possess certain characteristics that enhance its ability to remove nitrosamines from the tobacco. For example, in some embodiments, the nitrosamine-reducing material has a surface area greater than about 600 square meters per gram, and in some embodiments, greater than about 1000 square meters per gram. Moreover, in some embodiments, the nitrosamine-reducing material includes pores, channels, or combinations thereof, which have a mean diameter larger than about 3.5 angstroms, and in some embodiments, larger than about 7 angstroms.
The nitrosamine-reducing material can generally be contacted with the soluble portion in any of a variety of different ways. For example, in one embodiment, the nitrosamine-reducing material can be mixed with the soluble portion. If desired, after contacting the soluble portion with the nitrosamine-reducing material, the nitrosamine-reducing material may optionally be removed therefrom.
Besides being capable of reducing the content of nitrosamines in tobacco, it has also been discovered that the nitrosamine-reducing material is capable of reducing the content of alkaloids in the tobacco. For example, in some embodiments, the alkaloids content can be reduced at least about 10%, in some embodiments between about 25% to about 95%, and in some embodiments, between about 60% to about 95% after being contacted with the nitrosamine-reducing material.
Other features and aspects of the present invention are described in more detail below.